P1141: IBRUTINIB AND RITUXIMAB AS FIRST LINE THERAPY FOR MANTLE CELL LYMPHOMA: A MULTICENTRE, REAL-WORLD UK STUDY
Authors: A. Tivey, R. Shotton, T. A. Eyre, D. Lewis, N. Crosbie, E. Nga, R. Guerrero Camacho, W. Swe, H. Marr, C. Rees, S. Moule, T. Sutton, D. Wrench, N. Thomas, M. Wilson, J. Bailey, M. Prahladan, A. Hodson, M. Koppana, S. Smith, S. Jones, F. Miall, J. Norman, E. Davies, C. Hildyard, L. Lowry, S. Paneesha, I. Qureshi, A. Beech, C. Bedford, A. Everden, D. Tucker, J. Wright, J. Goddard, T. Nicholson, J. Wilson, A. Lord, B. Jackson, M. Flont, A. Gibb, K. Linton
Journal: HemaSphere (2022)

Background: Ibrutinib (IBR) is an oral covalent Bruton tyrosine kinase inhibitor (BTKi), licensed for treatment of relapsed or refractory mantle cell lymphoma (MCL). Under NHS interim Covid-19 agreements in England, IBR with or without rituximab (R) was approved for the frontline treatment for MCL patients (pts) as a safer alternative to conventional immunochemotherapy. Although recent phase 2 studies have reported high response rates in low-risk patients for this combination in the frontline setting, randomised phase 3 and real-world data are currently lacking. Aims: To describe the real-world response rates (overall response rate (ORR), complete response (CR) rate) and toxicity profile of IBR +/- R in adult patients with previously untreated MCL. Methods: Following institutional approval, adults commencing IBR +/- R for untreated MCL under interim Covid-19 arrangements were prospectively identified by contributing centres. Hospital records were interrogated for demographic, pathology, response, toxicity and survival data. ORR/CR were assessed per local investigator according to the Lugano criteria using CT and/or PET-CT. Results: Data were available for 66 pts (72.7% male, median age 71 years, range 41-89). Baseline demographic and clinical features are summarised in Table 1. 23/66 pts (34.8%) had high-risk disease (defined as presence of TP53 mutation/deletion, blastoid or pleomorphic variant MCL, or Ki67%/MiB-1 ≥30%). IBR starting dose was 560mg in 56/62 pts (90%) and was given with R in 22/64 pts (34%). At a median follow up of 8.7 months (m) (range 0-18.6), pts had received a median of 7 cycles of IBR. 19/60 pts (32%) required a dose reduction or delay in IBR treatment. New atrial fibrillation and grade ≥3 any-cause toxicity occurred in 3/59 pts (5.8%) and 8/57 (14.0%) respectively. For the whole population and high-risk pts only, ORR was 74.4% and 64.7% respectively (p=0.2379), with a median time to response of 3.8m, coinciding with the first response assessment scan. Seven pts (16.7%), of whom 2 had high-risk disease, attained CR at a median of 6.0m. ORR for pts receiving vs not receiving R were 84.2% and 66.7% respectively (p=0.1904). IBR was discontinued in 20/61 pts (32.8%) at a median time to discontinuation of 4.1m, due to progressive disease (PD, 19.7%), toxicity (4.9%), death (3.3%; 1 pt each of Covid-19 and E. coli infection), pt choice (3.3%) and other unspecified reasons (1.6%). 15/66 pts (22.7%) overall and 7/23 (30.4%) with high-risk disease progressed on IBR at a median time to PD of 4.0m. No pts underwent autologous stem cell transplantation consolidation during the study period. 12/57 pts (21.1%) received second line treatment (R-chemotherapy n=7, Nordic MCL protocol n=2, VR-CAP n=2, pirtobrutinib n=1). Response to second line treatment was CR in 4/11 pts, PD in 7/11. Of the 2 Nordic-treated patients, 1 had CR after cycle 2 and 1 PD. Fourteen pts (21.2%) died during the follow up period, due to MCL (n=11), Covid-19 (n=2) and congestive cardiac failure (n=1). Overall survival was lower for patients with high-risk disease (HR 0.55, p=0.038). Image:Summary/Conclusion: In this real-world UK cohort of pts receiving first-line IBR +/-R for MCL, including older and high-risk pts, we report high ORR rates in a similar range to the phase II Geltamo IMCL-2015 study of combination IBR-R in an exclusively low-risk population. Documented CR rates were lower, possibly reflecting a low usage of rituximab in the Covid-19 pandemic as well as CT assessment of response. Treatment was generally well tolerated, with low rates of toxicity-related treatment discontinuation. The study is ongoing.